Reynolds Creek Exp Watershed NPP data sets
November 17, 2020
Reynolds Creek Experimental Watershed
- data source: Data was provided on 11/17/2020 by Pat Clark.
- Info on the site can be found at the Northwest Watershed Research Center and with other data associated with the critical zone observatory datasets.
ANPP method: double-sampling, weight estimate method described by Wilm et al. (1944).
Chris explanation: two visual estimates by researchers on 10 inside/10 outside plots, corrected by weighed samples from 3 plots.
Methods: Fenced exclosures were established at each study site in 1971 and 1972 to exclude livestock. The area around the exclosures were grazed as part of the existing allotment or pasture. Grazing intensities were usually moderate, except at the Nettleton site where an intensive, heavy grazing treatment was imposed over a ten-day period each June. The annual herbage yield sampling plots on the grazed areas were protected by small wire cages, which were randomly located each spring prior to any grazing.
Annual herbage yields were determined by the double-sampling, weightestimate method described by Wilm et al. (1944). Each year, two people estimated the green herbage weight, by species, within 20 randomly located, 9.6 m2 circular plots at each site – 10 plots inside and 10 plots outside fenced exclosures. After the weight estimates were made, three plots were clipped by species to determine dry weight correction factors, and all yields were reported on the basis of an air-dry weight of 12 percent moisture. Yield estimates were made at each site when bottlebrush squirreltail (Sitanion hysterix) had reached the seed set stage. Only the nonwoody portion of the brush species was considered annual growth.
Basal and canopy cover were obtained from seven 100-point transects in both the grazed and nongrazed treatments at each site, at the same time yield estimates were made. The point data were taken by the wheel-point method described by Tidmarsh and Havenga (1915), and von Broembsen (1965).
A wheel-point contacted the ground every 24 inches along the sampling transect. A ground level and up to three overstory hits were recorded counting from the ground up after the spoke was vertical. All ground level vegetation hits were considered basal cover. Only the first three overstory hits were recorded. If the same species was hit more than once per pin, only the first hit was recorded. Plant hits were recorded when any part of the pin contacted a plant part. In 1974, 1975, 1978, and 1979, additional transects were taken near the end of the grazing season.
Frequency of occurrence was determined by dividing the total number of hits by the number of point quadrats (pins) where not more than one hit per species was recorded for each point quadrat.
An analysis varience was used to determine mean yield differences at the 10 percent probability level. The T-test was used to determine mean cover differences at the 5 percent probability level.
- Abstract or other: Results of an eleven year study on the Reynolds Creek Watershed in southwest Idaho showed that excluding grazing did not increase forage production. At one site where the grazing treatment consisted of heavy grazing for a few weeks each summer, the nongrazed exclosure produced more than the grazed area. In general, basal cover of grasses, forbs, shrubs, litter, rock, and bare ground was not measurably different between the grazed and nongrazed treatments. Only the heavy grazing treatment reduced litter and increased percent bare ground by a statistically significant amount. There were some statistically different cover conditions at other sites, but none of the differences were consistent between sites or treatments at sites.
- Primary publication: Forage Production, Botanical Composition, and Ground Cover as Affected by Excluding Grazing in Southwest Idaho
- By: Clayton L. Hanson, Clifton W. Johnson, J. Ross Wight, Gilbert A.Schumaker, and Delbert L. Coon
- Published at: ARS, Western Region Series
- Secondary pub: climate data from Hanson, Marks, and Van Vactor, 2001. Long-term climate database, Reynolds Creek Experimental Watershed, Idaho, United States. Water Resources Research, vol 37, no 11, 2839-2841.
Note, interagency plant species code uses an older version and thus may not line up with newer versions.
There are more species level plots for the sites, only included a few for cleanliness.